Systems and methods for cutting a tubular member

ABSTRACT

A closure device for cutting a tubular member includes a housing, and a cutting member disposed in the housing, wherein the cutting member is coupled to a heating element, wherein the cutting member is configured to transfer heat to a tubular member from the heating element to cause a loss of mechanical integrity of the tubular member as the cutting member physically engages the tubular member.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Hydrocarbon drilling systems utilize drilling fluid or mud for drilling a wellbore in a subterranean earthen formation. Drilling systems often utilize a blowout preventer (BOP) stack or system to seal, control, and monitor the wellbore to prevent an uncontrolled release of wellbore fluids to the surrounding environment, such as in the event of an uncontrolled influx of fluid from the formation into the wellbore. BOP stacks may comprise one or more actuatable valves or mechanical devices, such as ram and annular BOPs. In offshore applications, the BOP stack may further include electrical and hydraulic lines, control pods, hydraulic accumulators, kill and choke lines, and a support frame. Ram BOPs of the BOP stack typically comprise a pair of opposed rams that are actuated rectilinearly towards a central throughbore or chamber of the ram BOP, where the rams of the ram BOP may comprise, among others, pipe rams for closing around a drill pipe extending through the central throughbore, shear rams for shearing a drill pipe extending through the central throughbore, and blind shear rams for both shearing the drill pipe and sealing the wellbore. Drilling systems employing relatively longer and deeper wellbores, including deviated wellbores, may employ higher-strength drill pipe comprising a larger size and/or wall thickness. These systems may necessitate the use of larger, more powerful shear rams configured for shearing larger, higher-strength drill pipe. Moreover, the use of higher-strength drill pipe may increase the time required by the shear rams to successfully shear the drill pipe in response to the actuation of the ram BOP.

SUMMARY

An embodiment of a closure device for cutting a tubular member comprises a housing, and a cutting member disposed in the housing, wherein the cutting member is coupled to a heating element, wherein the cutting member is configured to transfer heat to a tubular member from the heating element to cause a loss of mechanical integrity of the tubular member as the cutting member physically engages the tubular member. In some embodiments, the cutting member is configured to unequally distribute a thermal flux from the heating element to the tubular member along a partial circumference of the tubular member. In some embodiments, the cutting member is configured to transfer heat to a tubular member from the heating element using thermal conduction when the cutting member physically engages the tubular member. In certain embodiments, the closure device further comprises a retaining member frangibly coupling the heating element to the cutting member. In certain embodiments, the heating element comprises an induction heating element. In some embodiments, the heating element forms a cutting edge of the cutting member. In some embodiments, the closure device further comprises a thermal insulator disposed between the heating element and the cutting member. In certain embodiments, the closure device further comprises a power supply connected to the heating element and configured to store and selectably transfer energy to the heating element.

An embodiment of a closure device for cutting a tubular member comprises a housing, a heating element disposed in the housing, and a cutting member slidably disposed in the housing, wherein the heating element is configured to unequally distribute a thermal flux along a circumference of the tubular member when the cutting member physically engages the tubular member. In some embodiments, the cutting member is configured to transfer heat to a tubular member from the heating element using thermal conduction when the cutting member physically engages the tubular member. In some embodiments, the closure device comprises a ram blowout preventer and the cutting member comprises a ram block. In certain embodiments, the closure device further comprises a telescoping member extending between a bonnet and a slidable piston of the blowout preventer, wherein the telescoping member is configured to extend and retract as the piston is displaced through the blowout preventer, and a power cable electrically connected with the heating element, wherein the power cable is disposed about the telescoping member. In certain embodiments, the bonnet comprises a recess extending therein, and the telescoping member extends between the recess and the slidable piston. In some embodiments, the closure device further comprises a power supply connected to the heating element and configured to store and selectably transfer energy to the heating element. In some embodiments, the power supply comprises a capacitor array. In certain embodiments, the closure device further comprises a sensor disposed in the housing and configured to detect physical engagement between the cutting member and the tubular member, and a controller connected to the sensor and power supply, wherein the controller is configured to cause the power supply to transfer energy to the heating element in response to receiving a signal from the sensor indicating physical engagement between the cutting member and the tubular member. In certain embodiments, the heating element comprises an inductive heating element.

An embodiment of a method for cutting a tubular member comprises engaging an engagement portion of a tubular member with a cutting member, energizing a heating element, transferring heat from the heating element to the engagement portion of the tubular member via thermal conduction between the cutting member and the tubular member, and physically cutting the tubular member with the cutting member. In some embodiments, the engagement portion extends along only a portion of the circumference of the tubular member. In some embodiments, the method further comprises unequally distributing a thermal flux along a circumference of the tubular member. In certain embodiments, the method further comprises physically engaging the tubular member with the heating element, wherein the heating element is coupled to the cutting member. In certain embodiments, the method further comprises frangibly decoupling the heating element from the cutting member in response to the heating element fusing to the tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments, reference will now be made to the accompanying drawings in which:

FIG. 1 is a schematic view of an embodiment of a drilling system including an embodiment of a BOP stack in accordance with principles disclosed herein;

FIG. 2 is a cross-sectional perspective view of an embodiment of a ram BOP of the BOP stack of FIG. 1 in accordance with principles disclosed herein;

FIG. 3 is a cross-sectional, schematic top view of the ram BOP of FIG. 2;

FIG. 4 is an enlarged view of the cross-sectional view of FIG. 3;

FIG. 5 is a cross-sectional top view of another embodiment of a ram BOP in accordance with principles disclosed herein;

FIG. 6 is a cross-sectional side view along lines 6-6 of FIG. 5 of the ram BOP of BOP of FIG. 5;

FIG. 7 is an enlarged view of the cross-sectional view of FIG. 6 of the ram BOP of FIG. 5; and

FIG. 8 is a flowchart showing an embodiment of a method for inductively cutting a tubular member in accordance with principles disclosed herein.

DETAILED DESCRIPTION

In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the disclosed embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.

Unless otherwise specified, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.

FIG. 1 is a schematic diagram illustrating an embodiment of a drilling system 10. In an embodiment, drilling system 10 comprises a system for cutting a tubular member, such as a drill pipe, by reducing the mechanical integrity of the tubular member through inductive heating. The drilling system 10 can be configured to extract various minerals and natural resources, including hydrocarbons (e.g., oil and/or natural gas), or configured to inject substances into a sea floor 3 and a subterranean earthen formation 5 via a well or wellbore 7. In this embodiment, drilling system 10 generally includes a drilling vessel 12 disposed at a surface or waterline 9, a wellhead 18 secured to the sea floor 3 via a casing conductor 20 that extends into the formation 5, a marine riser 16 extending towards the sea floor 3 from the drilling vessel 12, and a blowout preventer (BOP) assembly 30 disposed beneath the waterline 9 and connected to a lower end of the riser 16. In this embodiment, vessel 12 is a floating platform, and thus, may also be referred to as platform 12, and includes a drilling derrick 14. In other embodiments, the vessel (e.g., vessel 12) can be a drill ship or any other vessel disposed at the sea surface for conducting offshore drilling and/or production operations.

In this embodiment, BOP assembly 30 includes a pair of closure devices or ram BOPs 100 coupled to the upper end of wellhead 18 and a lower marine riser package (LMRP) 32 connected to the lower end of marine riser 16. During drilling operations, riser 16 takes drilling/formation fluid returns to platform 12. Further, riser 16 is coupled to electrical and hydraulic lines (not shown) for powering and controlling the actuation of components of BOP assembly 30, including ram BOPs 100. BOP assembly 30 is generally configured to provide emergency pressure control of drilling/formation fluid in the wellbore 7 should a sudden pressure surge escape the formation 5 into the wellbore 7. BOP assembly 30 may thereby prevent damage to the drilling vessel 12 and the marine riser 16 from fluid pressure exiting wellhead 18. In this embodiment, BOP assembly 30 also includes a frame 34 for physically supporting components of BOP assembly 30, including ram BOPs 100, and a plurality of accumulators 36 configured to provide backup hydraulic fluid pressure for actuating components of BOP assembly 30, such as ram BOPs 100. Although ram BOPs 100 are shown in FIG. 1 as forming a part of offshore drilling system 10, in other embodiments, ram BOPs 100 may be utilized in other applications, such as conventional, land based drilling systems.

Referring to FIGS. 2-4, a cross-sectional perspective view of one of the ram BOPs 100 of BOP assembly 30 is shown. In this embodiment, ram BOP 100 generally includes a body or housing 102 and a pair of bonnet assemblies 108. Housing 102 of ram BOP 100 includes a longitudinally extending throughbore 104 and laterally extending ram guideways 106. Each bonnet assembly 108 is coupled or mounted to the housing 102 with fasteners 110 and aligned with ram guideways 106. Housing 102 includes a laterally extending fluid passage 102P in fluid communication with the throughbore 104 of housing 102. Each bonnet assembly 18 includes an actuation assembly 112 configured to actuate ram BOP 100 between an open position (shown in FIG. 2) allowing for the continuous passage of a tubular member or drill pipe 40 through throughbore 104, and a closed position restricting the continuous passage of drill pipe 40 through throughbore 104. Further, in this embodiment, in the open position of ram BOP 100 the passage of a fluid flow through throughbore 104 is permitted, while in the closed position, the passage of fluid flow through throughbore 104 is restricted. In this embodiment, each actuation assembly 112 generally includes an operating cylinder 113, a piston 114, a connecting rod 116, and a cutting member or ram block 118. While only one ram guideway 106 and actuation assembly 112 are completely shown in FIG. 2, it is understood by those of ordinary skill in the art that there is a pair of ram guideways 106 and actuation assembly 112. The connecting rod 116 of each actuation assembly 112 extends between and couples with a corresponding piston 114 and ram block 118. In this arrangement, hydraulic pressure may be inputted to the cylinders 113 to apply fluid pressure against the pistons 114 disposed therein to displace the pistons 114 through cylinders 113, thereby displacing the coupled ram blocks 118 into or out of the throughbore 104 of housing 102 to actuate ram BOP 100 between the open and closed positions.

Referring to FIGS. 2-4, in this embodiment, ram BOP 100 comprises a blind shear ram BOP, and thus, ram blocks 118 are configured to physically engage and shear drill pipe 40 extending through throughbore 104 of housing 102 until drill pipe 40 is sheared into two separate pieces. Particularly, each ram block 118 includes a cutting edge 120 for physically engaging an outer surface 42 of the drill pipe 40, where drill pipe 40 extends through the marine riser 16, BOP assembly 30, and wellhead 18 of drilling system 10 shown in FIG. 1. Further, in this embodiment, ram blocks 118 include seals 122 for sealing against an inner surface of ram guideways 106. In this manner, when ram BOP 100 is actuated into the closed position cutting or shearing drill pipe 40, flow is restricted through an inner throughbore 44 of drill pipe 40 and an annulus 46 formed between the outer surface 42 of drill pipe 40 and the inner surface of the throughbore 104 of housing 102.

As shown particularly in FIGS. 3 and 4, in this embodiment, each actuation assembly includes an inductive heating assembly 200 generally configured to heat an engagement portion or interface 40 c (shown in FIG. 4) of drill pipe 40 when ram BOP 100 is actuated into the closed position and the cutting edge 120 of each ram block 118 shears the drill pipe 40. Although FIG. 3 illustrates each actuation assembly 112 of ram BOP 100 as including an inductive heating assembly 200, in other embodiments, only one of the actuation assemblies 112 of ram BOP 100 may include an inductive heating assembly 200. Further, although in this embodiment inductive heating assembly 200 is utilized with blind shear ram BOP 100, in other embodiments, inductive heating assembly 200 may be utilized in shear ram BOPs that are not configured to seal a throughbore extending therethrough (i.e., are not “blind” shear ram BOPs), or in other components of drilling systems actuatable to shear, cut, or sever a member, such as a tubular member or drill pipe.

Particularly, each inductive heating assembly 200 is configured to heat the engagement portion 40 c of drill pipe 40 to be cut by ram blocks 118 to a temperature sufficient to cause a loss of mechanical integrity in drill pipe 40, such as by weakening or decreasing the yield strength the engagement portion 40 c of drill pipe 40, thereby reducing the necessary pressure force applied against piston 114 and/or the necessary time required to completely cut engagement portion 40 c of drill pipe 40 by ram block 118. In this manner, given that the force required to cut drill pipe 40 is reduced via the reduction of mechanical integrity of drill pipe 40, the hydraulic pressure necessary to cut drill pipe 40 via ram blocks 118 is also reduced. Thus, the necessary hydraulic pressure supplied to cylinders 113 of ram BOP 100 (i.e., the operating pressure of ram BOP 100) for cutting drill pipe 40 is thereby minimized. In certain embodiments, the inductive heating assembly 200 of each actuation assembly 112 is configured to heat the engagement portion 40 c of drill pipe 40 to an annealing temperature of the material (e.g., steel) comprising drill pipe 40. In certain embodiments, the inductive heating assembly 200 of each actuation assembly 112 is configured to heat the engagement portion 40 c of drill pipe 40 to a high temperature austenite phase of the material (e.g., steel) comprising drill pipe 40.

In this embodiment, the inductive heating assembly 200 of each actuation assembly 112 generally includes a heating element 202, a thermal insulator, 210, conductors 220, 222, and 224, an inductive coupler 230, a power supply 240, a sensor 244, and a controller 260. The heating element 202 of each inductive heating assembly 200 is configured to rapidly heat engagement portion 40 c of drill pipe 40 in response to receiving energy from the power supply 240, where the power is transferred from the power supply 240 to the heating element 202 via conductors 220, 222, 224, and inductive coupler 230. In this embodiment, conductors 220, 222, and 224 comprise insulated electric cables; however, in other embodiments, conductors 220, 222, and 224 may comprise other electrical conductors known in the art, such as busbars, etc. In this arrangement, heating element 202 comprises the cutting edge 120 of each ram block 118. In this embodiment, the heating element 202 of each inductive heating assembly 200 comprises an induction heating element configured to rapidly heat engagement portion 40 c of drill pipe 40 in response to receiving electrical power from power supply 240 and generally includes a conductor, an electromagnet, and an electronic oscillator (not shown) for passing a high-frequency alternating current through the electromagnet and generating eddy currents in the conductor that produce heat through ohmic heating; however, in other embodiments, heating element 202 may comprise other heating elements known in the art.

The thermal insulator 210 of each inductive heating assembly 200 is generally configured to limit or decrease the amount of flux of thermal energy from the heating element 202 to the material composing ram block 118, where the thermal energy produced by heating element 202 could potentially jeopardize the mechanical properties of ram block 118. Thus, thermal insulator 210 is configured to restrict the passage of thermal energy from heating element 202 to ram block 118 such that the material (e.g., steel) comprising ram block 118 is not damaged nor the mechanical properties of the material comprising ram block 118 materially degraded so as to jeopardize the operation of ram block 118 when ram BOP 100 is actuated into the closed position. The thermal insulator 210 of each inductive heating assembly 200 is coupled or attached to an attachment surface 118 s of ram block 118, thereby interposing thermal insulator 210 between heating element 202 and ram block 118 such that heating element 202 does not directly contact ram block 118.

In this embodiment, thermal insulator 210 comprises a composite ceramic material; however, in other embodiments, thermal insulator 210 may comprise other materials known in the art suitable for restricting or limiting heat transfer between the heating element 202 and ram block 118. In still further embodiments, the inductive heating assembly 200 of each actuation assembly 112 may not include a thermal insulator, and instead, the ram block 118 of each actuation assembly 112 may comprise a material (e.g., temperature resistant steel, etc.) configured for operation at high temperatures.

The inductive coupler 230 is configured to pass the electrical power provided by power supply 240 from external conductor 224, which is disposed exterior of housing 102 and connects with power supply 240, to internal conductor 222, which is disposed within housing 102 of ram BOP 100, and connects with heating element 202. In this embodiment, inductive coupler 230 comprises a first or outer annular inductive coupler 232, and a second or inner annular inductive coupler 234. The outer inductive coupler 232 is disposed along an inner surface 113 s of cylinder 113. The inner inductive coupler 234 is disposed along an outer surface 114 s of piston 114, and thereby is disposed directly adjacent with, or physically contacts, the outer inductive coupler 232. Also, the outer inductive coupler 232 extends longitudinally along the inner surface 108 s of bonnet 108 a sufficient distance such that outer coupler 232 and inner coupler 234 remain positioned directly adjacent in both the open and closed positions of ram BOP 100. In this manner, electrical power may be communicated across inductive coupler 230 as ram BOP 100 is actuated from the open position into the closed position.

In this embodiment, each inductive coupler 232 and 234 of inductive coupler 230 generally includes an electrical conductor coiled about a magnetic member such that an electrical current applied to the conductor of one inductive coupler (232 or 234) is induced in the corresponding inductive coupler (232 and 234) via the physical proximity of the inductive couplers 232 and 234, obviating the need of passing an electrical conductor between the piston 114 and bonnet 108. However, in other embodiments, inductive coupler 230 may comprise other couplers known in the art that are configured for passing electrical power without requiring the passage of an electrical conductor. Moreover, in still further embodiments, the inductive heating assembly 200 of each actuation assembly 112 may include a single electrical conductor extending between the power supply 240 and heating element 202.

The power supply 240 of each inductive heating assembly 200 is configured to rapidly provide electrical power to the corresponding heating element 202 sufficient to heat the engagement portion 40 c of drill pipe 40 to a degree sufficient to reduce the mechanical integrity of the material comprising drill pipe 40 at the engagement portion 40 c. Particularly, in certain embodiments, power supply 240 of each inductive heating assembly 200 is configured to rapidly provide electrical power to the corresponding heating element 202 sufficient to heat the engagement portion 40 c of drill pipe 40 to the annealing temperature of the material comprising drill pipe 40. In certain embodiments, the power supply 240 of each inductive heating assembly 200 is coupled to the BOP assembly 30. In other embodiments, each power supply 240 is located on a separate subsea skid disposed proximal to BOP assembly 30. In still further embodiments, each power supply 240 is disposed on the drilling platform 12. In this embodiment, each power supply 240 comprises a capacitor array configured to store and selectably rapidly discharge or release electrical power. In other embodiments, each power supply 240 comprises other mechanisms for storing and rapidly releasing energy, which may be electrical energy or other forms of energy convertible to electrical energy. For instance, in certain embodiments, each power supply 240 may comprise one or more accumulators driving an electrical generator, a fuel cell powered by solid state Hydrogen, and other power storage and discharge mechanisms known in the art.

As will be explained further herein, the sensor 244 of each inductive heating assembly 200 is configured to detect physical contact or engagement between a corresponding ram block 118 and the outer surface 42 of drill pipe 40. Each sensor 244 is coupled to a corresponding ram block 118 and is connected to a power supply 240 via a cable 246. In this embodiment, each sensor 244 comprises a strain gauge configured to detect strain in the corresponding ram block 118; however, in other embodiments, sensors 244 may comprise other sensors or detectors known in the art for detecting engagement between ram blocks 118 and drill pipe 40. For instance, in other embodiments sensors 244 may comprise optical detectors mounted to the housing 102 of ram BOP 100 and configured to optically detect physical engagement between ram blocks 118 and drill pipe 40. Each inductive heating assembly 200 includes a controller 260 comprising a processor and memory, where controller 260 is connected with power supply 240 and sensor 244 and is configured for controlling the transfer of energy from power supply 240 to heating element 202 in response to a signal transmitted from sensor 244, as will be discussed further herein. Further, although in this embodiment each inductive heating assembly 200 includes a sensor 244 and a controller 260, in other embodiments, inductive heating assembly 200 may not include sensor 244 and controller 260.

Referring to FIGS. 5-7, another embodiment of a ram BOP 300 including an inductive heating assembly 350 is shown. In this embodiment, ram BOP 300 generally includes a BOP body 302, a bonnet 310, a piston 324 connected to a connecting rod 330, and a ram block 340 coupled to connecting rod 330. BOP body 302 has a central bore 304 in which ram block 340 is slidably disposed and a central passage 306 through which connecting rod 330 extends. In this embodiment, bonnet 310 is coupled to body 302 and includes a head 312 disposed at a terminal end thereof and a chamber 314 in which piston 324 is slidably disposed. Bonnet 310 also includes a recess 316 extending into head 312 from chamber 314 and a cable passage 318 extending through head 312. Bonnet 310 further includes a first or piston close port 320 and a second or piston open port 322, where ports 320 and 322 are each in fluid communication with chamber 314.

Piston 324 is coupled to a first or outer terminal end of connecting rod 330, and in certain embodiments, includes an annular seal disposed on an outer surface thereof for sealingly engaging an inner surface of chamber 314. In this arrangement, the sealing engagement between piston 324 and the inner surface of chamber 314 divides chamber 314 into a first chamber 314 a and a second chamber 314 b, where piston close port 320 provides fluid communication to first chamber 314 a while piston open port 322 provides fluid communication to second chamber 314 b. Thus, flowing pressurized fluid into first chamber 314 a via piston close port 320 causes piston 324 to shift or be displaced into a closed position where piston 324 is disposed proximal BOP body 302, while following pressurized fluid into second chamber 314 b via piston open port 322 causes piston 324 to shift into an open position where piston 324 is disposed directly adjacent head 312 of bonnet 310.

Connecting rod 330 couples piston 324 with ram block 340 and includes a central passage 332 extending longitudinally therethrough and a connector 334 disposed at a terminal end thereof for coupling connecting rod 330 with ram block 340. In this embodiment, connector 334 comprises a radially expanded button or disc that is received within a corresponding recess of ram block 340. In certain embodiments, an inner surface of passage 306 of body 302 includes an annular seal disposed therein for sealingly engaging an outer surface of connecting rod 330 to restrict fluid communication between chamber 314 of bonnet 310 and bore 304 of body 302. In this embodiment, ram block 340 comprises a shear ram block for cutting a tubular member, such as a drill pipe, extending through ram BOP 300, and generally includes a first receptacle 342, a cutting edge 344 that is configured to physically engage and cut the aforementioned tubular member, a cable passage 346 extending from first receptacle 342, and a second receptacle 348 extending along cutting edge 344. While in this embodiment ram block 340 comprises single cable passage 346, in other embodiments, ram block 340 may comprise multiple passages for the disposal of multiple independent cables. In this arrangement, the connector 334 of connecting rod 330 is received within first receptacle 342 of ram block 340 to releasably couple connecting rod 330 with ram block 340.

Similar to the inductive heating assembly 200 discussed above, inductive heating assembly 350 is configured to heat an engagement portion or interface of the tubular member to be cut, such as engagement portion 40 c discussed above. In this embodiment, inductive heating assembly 350 generally includes a power connector 352, a coiled power cable 354, a telescoping member 355, a first or transmitting inductive coupler 356, a second or receiving inductive coupler 358, an insulator 360, a heating element 362, and a retaining plate or member 364. Power connector 352 is configured to receive power for heating the heating element 362 from a power supply, such as power supply 240 discussed above. Power received by power connector 352 is transmitted to heating element 362 via coiled power cable 354, inductive couplers 356 and 358, and a cable 366 (shown in FIGS. 6 and 7) extending between receiving coupler 358 and heating element 362. While in this embodiment an inductive coupling provided by couplers 356 and 358 transmits power between cable 354 and cable 366, in other embodiments, a hardwired connection may couple cable 354 with cable 366 in lieu of an inductive coupling. In still further embodiments, power may be transferred between heating element 362 and power connector 352 via one or more cables that extend through passages (not shown) in BOP body 302 instead of connecting rod 330.

In this embodiment, cable 354 comprises a coiled power cable to allow for slidable displacement of piston 324 within chamber 314 of bonnet 310. Further, when piston 324 is disposed in the open position directly adjacent head 312 of bonnet 310, coiled power cable 354 is received within recess 316 of bonnet 310 to prevent damaging cable 354 or restricting the displacement of piston 324. In this embodiment, coiled power cable 354 is disposed or coiled about telescoping member 355, which extends between head 312 and piston 324. Telescoping member 355 is configured to support power cable 354 and thereby prevent cable 354 from collapsing. Telescoping member 355 is also configured to expand and retract telescopically to allow piston 324 to be displaced through chamber 314. In this embodiment, telescoping member 355 is hollow and perforated, and thus, is fully immersed by fluid disposed in chamber 314. However, in other embodiments, inductive heating assembly 350 may not include a telescoping member for supporting coiled power cable 354.

Transmitting coupler 356 of inductive heating assembly 300 is disposed within a receptacle of the connector 334 of connecting rod 330 while receiving coupler 358 is disposed within first receptacle 342 of ram block 340. In this arrangement, inductive couplers 356 and 358 are disposed directly adjacent each other and are configured similarly to inductive coupler 230 discussed above. Thus, inductive couplers 356 and 358 are configured to inductively conduct power received from power connector 352 and transmit the power received therefrom to heating element 362 via cable 366. While in this embodiment power connector 352 provides a hardwired connection, in other embodiments, power connector 352 may comprise an inductive coupler for inductively coupling with an external power supply.

In this embodiment, insulator 360 and heating element 362 are received within the second receptacle 348 of ram block 340 that extends along the cutting edge 344 thereof. Similar to insulator 210 discussed above, insulator 360 is configured to restrict or decrease the amount of heat transferred from heating element 362 to the material comprising ram block 340. As with heating element 202 discussed above, heating element 360 is configured to transform electrical energy (such as the power received from power connector 352) into heat, which may be transferred to the engagement portion of a tubular member to be cut. In this embodiment, insulator 360 and heating element 362 are received within the second receptacle 348 of ram block 340 and releasably coupled or secured to ram block 340 via retaining plate 364. In certain embodiments, retaining plate 364 is releasably secured to ram block 340 via one or more fasteners 365 extending through retaining plate 364 and secured within ram block 340.

Further, in this embodiment, there is an offset 368 between cutting edge 344 of ram block 340 and an outer edge (e.g., the edge closest cutting edge 344) of retaining plate 364 to provide space for the fasteners 365 and to decrease the amount of heat transferred from heating element 362 to retaining plate 364, thereby maximizing the amount of heat transferred from heating element 362 to the engagement portion (e.g., engagement portion 40 c) of the tubular member to be cut. Further, in certain embodiments, retaining plate 364 is configured to provide a frangible connection between heating element 362 and ram block 340 such that heating element 362 may be released from ram block 340 in the event of heating element 362 fusing to the tubular member to be cut. Particularly, upon cutting the tubular member, the heat provided by heating element 362 may cause heating element 362 to fuse with the material comprising the cut tubular member. Thus, a frangible connection may be provided between heating element 362 and ram block 340 to allow heating element 362 to be released in the event of fusion or other coupling formed between heating element 362 and the tubular member to prevent damage from incurring to other components of ram BOP 300 and inductive heating assembly 350. In this manner, the heating element 362 may comprise a sacrificial component for protecting other components of inductive heating assembly 350.

Referring to FIGS. 1-3 and 7, FIG. 7 illustrates a method 400 of inductively shearing a tubular member. At block 402 of method 400, a closure device is actuated towards a closed position. In certain embodiments, block 402 comprises actuating ram BOP 100 from the open position (shown in FIG. 2), where continuous passage of drill pipe 40 through throughbore 104 of ram BOP 100 is permitted, and the closed position where continuous passage of drill pipe 40 through throughbore 104 of ram BOP 100 is restricted. Particularly, in this embodiment, block 402 comprises providing hydraulic pressure within the cylinder 113 against an outer face of the piston 114 of each actuation assembly 112, and thereby displacing the piston 114 and ram block 118 laterally towards the drill pipe 40 extending through the throughbore 104. In this embodiment, hydraulic pressure may be applied to the cylinder 113 of each actuation assembly 112 via one or more pumps disposed on the drilling platform 12, or via the accumulators 36 of BOP assembly 30. Although hydraulic pressure is utilized in the embodiment above to actuate piston 114, in other embodiments, piston 114 may be actuated through other mechanisms, such as an electrical motor for displacing piston 114.

At block 404 of method 400 a tubular member is physically engaged or contacted with a cutting member of the closure device. In certain embodiments, block 404 comprises physically engaging the outer surface 42 of drill pipe 40 with the cutting edge 120 of the ram block 118 of each actuation assembly 112. The engagement of the outer surface 42 of drill pipe 40 by the cutting edge 120 of each ram block 118 occurs during the process of actuating ram BOP 100 from the open position towards the closed position, as discussed above with respect to block 402. As the cutting edge 120 of each ram block 118 physically engages the outer surface 42 of drill pipe 40, each cutting edge 120 physically engages the engagement portion 40 c of drill pipe 40, where the engagement portion 40 c of drill pipe 40 comprises a pair of opposed semi-circular sections of drill pipe 40 contacted and physically engaged by the corresponding pair of cutting edges 120, as shown particularly in FIGS. 3 and 4. Thus, in this embodiment, engagement portion 40 c does not cover the entire circumference of drill pipe 40.

At block 406 of method 400, the cutting member of the closure device is energized or provided with energy from an energy or power source. In certain embodiments, block 406 comprises transferring energy stored in each power supply 240 to the corresponding heating element 202 so as to rapidly heat a tubular member to be cut, such as engagement portion 40 c of drill pipe 40. In this embodiment, electrical energy is not supplied to each heating element 202 until the cutting edge 120 of each ram block 118 physically engages or contacts the engagement portion 40 c of drill pipe 40; however, in other embodiments, energy may be transferred from each power supply 240 to the corresponding heating element 202 prior to physical engagement of the cutting edge 120 of each ram block 118 against the engagement portion 40 c of drill pipe 40. In this embodiment, sensors 244 are utilized to synchronize the energization of heating elements 202 with the engagement between ram blocks 118 and drill pipe 40. Particularly, in response to receiving a signal from sensor 244 indicating physical engagement between ram block 118 and drill pipe 40, controller 260 transmits a signal to power supply 240 to thereby transfer energy stored therein to heating element 202, which rapidly converts the electrical energy supplied thereto into heat. As each heating element 202 is heated, thermal energy is transferred from heating elements 202 to the engagement portion 40 c of drill pipe 40.

In embodiments where each heating element 202 comprises or forms the cutting edge 120 of a respective ram block 118, thermal energy or heat is transferred (indicated by arrows 250 in FIG. 4) from heating elements 202 to engagement portion 40 c via thermal conduction resulting from the physical contact between cutting edges 120 and the engagement portion 40 c of drill pipe 40. In this manner, energy is efficiently transferred between engagement portion 40 c of drill pipe 40 and heating elements 202 by minimizing heat loss to fluids disposed within throughbore 108. Moreover, contact between heating elements 202 and engagement portion 40 c of drill pipe 40 focuses the thermal energy transferred from heating elements 202 into the engagement portion 40 c of drill pipe 40. In other words, the thermal energy transferred from heating elements 202 is unequally distributed along the circumference of drill pipe 40, with the maximum thermal or heat flux 250 occurring along engagement portion 40 c. In certain embodiments, block 406 also comprises flowing an inert fluid or gas into throughbore 108 of housing 102 via passage 102P such that the inert gas is disposed about the drill pipe 40 and cutting edges 120 of ram blocks 118. In this manner, the cutting of drill pipe 40 by ram blocks 118 may occur in an inert environment, reducing the possibility of combustion taking place within throughbore 108. In other embodiments, other mechanisms may be employed to produce an inert environment within throughbore 108, such as by depleting oxygen within throughbore 108.

At block 408 of method 400, the tubular member is cut with the cutting member of the closure device. In certain embodiments, block 408 comprises cutting or shearing drill pipe 40 via the cutting edges 120 of ram blocks 118 until drill pipe 40 is completely severed and ram BOP 100 is disposed in the closed position. Particularly, in some embodiments, block 408 comprises initiating a cut or shear in engagement portion 40 c via the cutting edges 120 of ram blocks 118. Given that engagement portion 40 c comprises the portion of the circumference of drill pipe 40 that is physically engaged by and initially cut by cutting edges 120, focusing the thermal energy transfer in engagement portion 40 c efficiently utilizes the heat provided by heating elements 202 by maximizing the reduction in mechanical integrity in the portion (e.g., engagement portion 40 c) of drill pipe 40 initially cut by cutting edges 120. In some embodiments, block 408 comprises frangibly decoupling the heating element (e.g., heating element 362) from the cutting member (e.g., ram block 340) via a frangible connection therebetween (e.g., retaining plate 364) in response to fusion between the heating element and the tubular member.

By maximizing thermal flux 250 into engagement portion 40 c, a relatively lesser amount of energy may be transferred to heating elements 202 from power supplies 240 while still providing a sufficient degree of thermal energy to engagement portion 40 c to allow cutting edges 120 of ram blocks 118 to initiate a cut or shear in engagement portion 40 c of drill pipe 40. Once a cut has been initiated in engagement portion 40 c, the mechanical integrity of drill pipe 40 along the circumference of which engagement portion 40 c is disposed will be decreased due to the stress risers provided by the initial physical cuts made by ram blocks 118, decreasing the amount of cutting force required to complete the shearing of drill pipe 40. Thus, concentrating the thermal flux 250 into engagement portion 40 c such that the thermal flux 250 into drill pipe 40 is not equally distributed about the circumference of drill pipe 40 may reduce the amount of energy required to be transferred to heating elements 202 to successfully cut or shear drill pipe 40. Further, although method 400 is described above in the context of ram BOP 100, the steps of method 400 may also be performed utilizing ram BOP 300 illustrated in FIGS. 5-7 and described above.

The above discussion is meant to be illustrative of the principles and various embodiments of the present disclosure. While certain embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The embodiments described herein are exemplary only, and are not limiting. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. 

What is claimed is:
 1. A closure device for cutting a tubular member, comprising: a housing; and a cutting member disposed in the housing, wherein the cutting member is coupled to a heating element; wherein the cutting member is configured to transfer heat to a tubular member from the heating element to cause a loss of mechanical integrity of the tubular member as the cutting member physically engages the tubular member.
 2. The closure device of claim 1, wherein the cutting member is configured to unequally distribute a thermal flux from the heating element to the tubular member along a partial circumference of the tubular member.
 3. The closure device of claim 1, wherein the cutting member is configured to transfer heat to a tubular member from the heating element using thermal conduction when the cutting member physically engages the tubular member.
 4. The closure device of claim 1, further comprising a retaining member frangibly coupling the heating element to the cutting member.
 5. The closure device of claim 1, wherein the heating element comprises an induction heating element.
 6. The closure device of claim 1, wherein the heating element forms a cutting edge of the cutting member.
 7. The closure device of claim 6, further comprising a thermal insulator disposed between the heating element and the cutting member.
 8. The closure device of claim 1, further comprising a power supply connected to the heating element and configured to store and selectably transfer energy to the heating element.
 9. A closure device for cutting a tubular member, comprising: a housing; a heating element disposed in the housing; and a cutting member slidably disposed in the housing; wherein the heating element is configured to unequally distribute a thermal flux along a circumference of the tubular member when the cutting member physically engages the tubular member.
 10. The closure device of claim 9, wherein the cutting member is configured to transfer heat to a tubular member from the heating element using thermal conduction when the cutting member physically engages the tubular member.
 11. The closure device of claim 9, wherein the closure device comprises a ram blowout preventer and the cutting member comprises a ram block.
 12. The closure device of claim 11, further comprising: a telescoping member extending between a bonnet and a slidable piston of the blowout preventer, wherein the telescoping member is configured to extend and retract as the piston is displaced through the blowout preventer; and a power cable electrically connected with the heating element, wherein the power cable is disposed about the telescoping member.
 13. The closure device of claim 12, wherein the bonnet comprises a recess extending therein, and the telescoping member extends between the recess and the slidable piston.
 14. The closure device of claim 9, further comprising a power supply connected to the heating element and configured to store and selectably transfer energy to the heating element.
 15. The closure device of claim 14, wherein the power supply comprises a capacitor array.
 16. The closure device of claim 14, further comprising: a sensor disposed in the housing and configured to detect physical engagement between the cutting member and the tubular member; and a controller connected to the sensor and power supply, wherein the controller is configured to cause the power supply to transfer energy to the heating element in response to receiving a signal from the sensor indicating physical engagement between the cutting member and the tubular member.
 17. The closure device of claim 9, wherein the heating element comprises an inductive heating element.
 18. A method for cutting a tubular member, comprising: engaging an engagement portion of a tubular member with a cutting member; energizing a heating element; transferring heat from the heating element to the engagement portion of the tubular member via thermal conduction between the cutting member and the tubular member; and physically cutting the tubular member with the cutting member.
 19. The method of claim 18, wherein the engagement portion extends along only a portion of the circumference of the tubular member.
 20. The method of claim 18, further comprising unequally distributing a thermal flux along a circumference of the tubular member.
 21. The method of claim 18, further comprising physically engaging the tubular member with the heating element, wherein the heating element is coupled to the cutting member.
 22. The method of claim 18, further comprising frangibly decoupling the heating element from the cutting member in response to the heating element fusing to the tubular member. 